<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>删除节点</title>
</head>
<body>
    <button>删除</button>
    <ul>
        <li>熊大1</li>
        <li>熊大2</li>
        <li>熊大3</li>
    </ul>
    <script>
        var ul = document.querySelector('ul')
        var btn = document.querySelector('button')
        btn.onclick = function() {
            // 判断 ul 里面 时候有 li
            if (ul.children.length === 0) {
                this.disabled = true;
            }
            else{
                // 删除 ul 里面第一个 li  
                ul.removeChild(ul.children[0])
            }
        }
    </script>
</body>
</html>